Cellulose‐Reinforced Programmable and Stretch‐Healable Actuators for Smart Packaging

Biomimetic actuators are promising candidates for smart soft robotics. The applications of state‐of‐the‐art actuators require the combination of programmable stimuli‐responsiveness, excellent robustness, and efficient self‐healing ability in a wide‐range of working conditions. However, these properties may be mutually exclusive. Inspired by biological tissues, two kinds of polyelectrolytes including polyvinyl alcohol (PVA) and polystyrene sulfonate (PSS) are exploited as the fillers of cellulose nanofibrils (CNFs) for the fabrication of the CNF/PVA/PSS (CAS) film via the assembly of the physically‐crosslinked network through multiple H‐bonding and electrostatic interactions. Achieved by a casting‐evaporation strategy, internal stress is stored within the polymer matrix and transforms into reversible anisotropic bending deformations in response to a humidity gradient. The speed, direction, and pitch of the bending can be programmed by tailoring the internal stresses and geometry of the samples. Moreover, the H‐bonded network also contributes to the effective energy dissipation toward high toughness during tensile stretching, as well as self‐healing ability during moisture saturation of the CAS films. This enables the fabrication of a humidity‐sensitive flower‐shaped actuator and self‐healable packaging paper. This study presents a biomimetic strategy for the fabrication of multi‐functional soft robotics, which holds great promise for applications in the fields of biosensors and smart packaging. A humidity‐responsive actuator with good programmability for tunable actuation response, high mechanical strength to withstand rupture, and the ability to self‐healin for long‐term usage are designed and fabricated. The smart devices fabricated from this cellulose‐reinforced actuator demonstrate promising potential in smart sensing and packaging materials.